Combine brown sugar, oil, egg, and vanilla. Mix well.
Stir in buttermilk, rhubarb and pecans..
In another bowl, sift together flour, baking powder, baking soda, and salt.
Add the dry ingredients to moist mixture, stir just to blend. Don’t over mix, batter will still be a little lumpy.

Fill prepared muffin cups 3/4 full with batter.
Sprinkle top of each muffin with cinnamon/sugar crumbs, a few more nuts.
Bake on center rack of oven at 350 degrees for 20 to 25 minutes (or at 375 degrees for 18-20 minutes). Toothpick test works on this recipe.
Makes a dozen really yummy muffins.